Concrete composition for underwater use

ABSTRACT

A concrete composition for underwater use contains about 0.1 to 4% by weight based on cement content of a water soluble vinyl polymer containing vinyl units having sulfonic groups. The concrete composition is easy to mix and prevents separation of concrete composition constituents as it is laid under water.

TECHNICAL FIELD

The present invention relates to a concrete composition for underwateruse. More specifically, the present invention relates to an underwaterconcrete which is easy to mix and which contains an admixture forpreventing separation of concrete composition constituents when concreteis laid under water.

The concrete composition according to the present invention includesmortar consisting of cement and sand, and concrete consisting of cement,sand, coarse aggregate and water.

BACKGROUND ART

As concrete is being laid under water, the cement paste portion iswashed away from a part of the concrete mix upon contact with water andthe concrete has a nonuniform composition, either as the concrete mix isfalling through the water or as the concrete mix is spreading in alateral direction. As a result, the strength of the concrete mix isreduced, and the separated cement paste is diffused into the surroundingwater rendering it turbid. In order to resolve these problems, in astructural material mixture for underwater structures, there isdisclosed a technique of adding to concrete a cellulose derivative orpolyacrylamide, i.e., an acrylamide homopolymer as an admixture(DE-O-No. 2541747). However, when such an admixture is used, theobtained concrete mix has a delayed setting time and a lower strength,particularly initially, than a concrete mix containing no such agent.

A concrete containing a polyacrylamide partial hydrolysate compound asdisclosed in Japanese Patent Disclosure No. 59-54656 has excellentcharacteristics as an underwater concrete in that it does not have adelayed setting time or a low initial strength. However, this polymercompound has a strong cohesive force with respect to cement as in thecase of an acrylamide homopolymer. Therefore, the concrete mix tends toharden and is difficult to mix. When mixing of the concrete mix isdifficult, mixing to obtain a uniform composition is time-consuming. Inaddition, the load on a mixer is increased, resulting in an impracticalconcrete composition.

A conventional method for adding a water soluble vinyl polymer to acement composition is known. For example, U.S. Pat. No. 4015991discloses as a water soluble vinyl polymer a hydrolysate of a copolymercontaining 2-acrylamido-2-methylpropane-sulfonic acid units. U.S. Pat.No. 4340525 discloses a copolymer containing vinyl sulfonic acid unitsas a water soluble vinyl polymer. However, such water soluble vinylpolymers are used in a cementing technique to prevent water in thecement composition from being absorbed in a porous stratum. Therefore,even if such a water soluble vinyl polymer is used in a technique forlaying concrete under water, the separation amount of cement continuesto be large and setting time of the concrete is still delayed.Therefore, when such a water soluble vinyl polymer is used in underwaterconcrete, the concrete mix cannot be prevented from deteriorating underwater. Furthermore, since the strength of the concrete mix is alsoconsiderably reduced, a water soluble vinyl polymer cannot be used as anunderwater concrete admixture.

DISCLOSURE OF INVENTION

The present inventors have made extensive studies to resolve theseproblems. As a result of these studies, it was found that a concretecomposition containing 0.1 to 4% by weight of a water soluble polymerbased on the weight of cement and containing units represented by ageneral formula (I): ##STR1## [wherein R₁ is a hydrogen atom or a loweralkyl group, A is --CH₂ --, --CONHCH₂ --, ##STR2## (wherein R₂ and R₃are a hydrogen atom or a lower alkyl group and can be the same ordifferent), or ##STR3## n is 0 or an integer of 1, and M is a hydrogenatom, alkali metal or ammonium]; or

0.1 to 4% by weight of a water soluble polymer based on the weight ofcement and containing vinyl units represented by the general formula (I)and having sulfonic groups, and containing vinyl units other than vinylunits having sulfonic groups and represented by a general formula (II):##STR4## [wherein R₄ is a hydrogen atom or a lower alkyl group, X is--CONH₂, --COOR⁵ (wherein R⁵ is a lower alkyl group or a lowerhydroxyalkyl group) or ##STR5## (wherein R⁶ and R⁷ are the same ordifferent lower alkyl group or such that when one is a hydrogen atom theother is a lower alkyl group; R⁶ and R⁷ can form 5- or 6-member ringstogether with nitrogen atoms bonded thereto with or without oxygenatoms)] is free from the problems associated with the conventionalconcrete composition and has desirable characteristics. It is,therefore, an object of the present invention to provide an underwaterconcrete composition which does not separate under water, has no settingtime delay or a decrease in strength, and allows easy mixing.

Examples of a vinyl monomer containing sulfonic groups and having thegeneral formula (I) may include 2-acrylamidoethane-sulfonic acid,2-acrylamidopropanesulfonic acid, 2-acrylamido-2-methylpropane-sulfonicacid, 2-methacrylamidoethanesulfonic acid,2-methylacrylamidopropanesulfonic acid,2-methacrylamido-2-methylpropanesulfonic acid, acrylamidomethanesulfonicacid, methacrylamidomethanesulfonic acid, vinylsulfonic acid,styrenesulfonic acid, or alkali metal salts or ammonium salts thereof.

Examples of a vinyl monomer having the general formula (II) may includeacrylamide, methacrylamide, N,N-dimethylacrylamide,N,N-diethylacrylamide, N-acryloylpiperidine, N-acryloylmorpholine,N,N-dimethylmethacrylamide, N,N-diethylmethacrylamide,N-methacryloylpiperidine, N-methacryloylmorpholine, N-methylacrylamide,N-ethylacrylamide, N-propylacrylamide, N-methylmethacrylamide,N-ethylmethacrylamide, N-propylmethacrylamide, methyl acrylate, ethylacrylate, hydroxyethyl acrylate, methyl methacrylate, ethylmethacrylate, and hydroxyethyl methacrylate.

A water soluble vinyl polymer compound to be used herein is prepared bypolymerizing a vinyl monomer represented by the general formula (I) by aknown method or by polymerizing a vinyl monomer represented by thegeneral formula (I) and a vinyl monomer represented by the generalformula (II) by a known method. Polymerization is preferably performedin an aqueous medium using a radial polymerization initiator such as aperoxide or an organic azo compound. The polymer can have a molecularweight of 1,000,000 to about 20,000,000 although it varies dependingupon the type and amount of the polymerization initiator used. When thepolymerization reaction is performed in an aqueous medium, the watersoluble vinyl polymer compound obtained may contain carboxyl groups.Therefore, the polymerization reaction is preferably performed in aneutral liquid or at a low temperature.

In a water soluble vinyl polymer compound used herein, when thecopolymerization ratio of the vinyl monomer represented by the generalformula (I) is increased, mixing of the concrete composition of thepresent invention is rendered easier. However, if this copolymerizationratio is too high, the water-inseparable property and compressivestrength of the concrete composition are decreased, resulting in adisadvantage. Therefore, the molar ratio of the acryl monomerrepresented by the general formula (I) to be subjected to thepolymerization reaction must be 3% or more and preferably 3 to 95%.

A water soluble vinyl polymer compound to be used herein must have ahigh molecular weight to impart the water-inseparable property to theconcrete composition. Thus, the molecular weight of the water solublevinyl polymer is preferably 1,000,000 or more. The water soluble vinylpolymer must be added at least in an amount of 0.1% by weight based onthe cement content of the concrete composition. When the amount of thewater soluble vinyl polymer exceeds about 4% by weight, it isuneconomical and also results in a viscous material which is hard tohandle and has a low compressive strength.

When a water soluble vinyl polymer compound is added to the concretecomposition of the present invention, it can be added to the cement inadvance, it can be added to the ready mixed concrete, or it can bedissolved and then added to the ready mixed concrete. At this time, aproper amount of a concrete dispersant such as a sulfonic acidderivative, e.g., melamine sulfonic acid-formaldehyde condensate,naphthalinesulfonic acid-formaldehyde condensate or lignin sulfonate canbe added to further improve concrete flow characteristics.

BEST MODE OF CARRYING OUT THE INVENTION Example 1

A vinyl monomer represented by the general formula (I) and a vinylmonomer represented by the general formula (II) were polymerized toprepare a water soluble acryl polymer having a molecular weight of about7,000,000. One % by weight of the polymer compound was added to aconcrete mix of the constituent proportions as illustrated in Table 1below based on the cement content thereof. The resultant mixture wasmixed with a uniaxial forced mixer having a volume of 50 l. The mixedstate was observed, and the mixture was subjected to the falling throughwater test and the compressive strength test.

                  TABLE 1                                                         ______________________________________                                        Unit amounts (kg/m.sup.3)                                                                        Water-  Sand-                                                             Fine    Coarse                                                                              cement                                                                              aggregate                                                                             Air                                               aggre-  aggre-                                                                              ratio ratio   content                            Water Cement   gate    gate  (%)   (%)     (%)                                ______________________________________                                        235   440      643     979   53    40      1                                  ______________________________________                                    

According to the falling through water test, a specimen concrete mix waspoured into a truncated container having a lower diameter of 5 cm, anupper diameter of 7 cm and a depth of 8 cm. The test was conducted byplacing the test container with the specimen concrete mix at a height of10 cm above the water surface in a cylindrical container having adiameter of 20 cm and a height of 26 cm and containing water therein toa depth of 16 cm, and then pouring the specimen concrete mix so as tolet it fall by gravity into the water. The test results were obtained bymeasuring a turbidity of the water by transmittance at a wavelength of660 μm with a photoelectric photometer. A higher transmittance means asmaller amount of cement component which has been separated from theconcrete and diffused into the water, and hence, smaller deteriorationof the concrete quality.

Specimens for the compressive strength test were prepared by forming theconcrete mix into the form of a cylinder having a diameter of 15 cm anda height of 30 cm and then curing it in water at 20° C. The tests werecarried out on the 7th and 28th day.

The mixing state of the concrete mix is indicated by the following threelevels.

A: Within 2 minutes after starting mixing of the concrete mix, a uniformmix with flowability is obtained. The mix has a desired slump value andis well mixed.

B: After mixing is started, the mix becomes temporarily hard. Within 7minutes, the mix achieves a uniform state having flowability and adesired slump value.

C: After mixing is started, the concrete mix coheres firmly and mixingis rendered difficult to perform. In order to obtain a uniform statewith flowability, a mixing time of longer than 7 minutes is required.

For the purpose of comparison, a similar test was performed for aconcrete mix (plain concrete) which did not contain a water solublevinyl polymer compound and for concrete mixes which contained 1% byweight of polyacrylamide (molecular weight: 7,000,000) and apolyacrylamide partial hydrolysate compound (molecular weight:7,000,000), respectively, based on the weight of the cement content.

The obtained results are shown in Table 2 below.

                  TABLE 2                                                         ______________________________________                                                                            Compressive                                                                   strength                                  Water                Trans-         (kg/cm.sup.2)                             soluble vinyl                                                                             Mixing   mittance Slump 7th   28th                                polymer compound                                                                          state    (%)      (cm)  day   day                                 ______________________________________                                        Example                                                                       Sodium 2-   A        99       21    257   370                                 acrylamido-2-                                                                 methylpro-                                                                    panesulfo-                                                                    nate-acryl-                                                                   amide co-                                                                     polymer                                                                       (10:90% mole)                                                                 Sodium 2-   A        98       21.5  253   361                                 acrylamido-                                                                   ethanesulfo-                                                                  nateacrylamide                                                                copolymer                                                                     (10:90% mole)                                                                 Sodium 2-   A        98       21    255   364                                 acrylamido-2-                                                                 methyl-pro-                                                                   panesulfonate-                                                                methacrylamide                                                                copolymer                                                                     (10:90% mole)                                                                 Sodium 2-   A        100      21.5  261   378                                 acrylamido-2-                                                                 methyl-pro-                                                                   panesulfonate-                                                                N,N--dimethyl-                                                                acrylamide                                                                    copolymer                                                                     (10:90% mole)                                                                 Comparative                                                                   Example                                                                       Polyacrylamide                                                                            C        89       19-20 140   280                                 Polyacrylamide                                                                            B        89       21.5  257   365                                 partial hydro-                                                                lysate com-                                                                   pound (6% mole                                                                hydrolysis                                                                    degree)                                                                       No admixture                                                                              A         3       22    257   358                                 ______________________________________                                    

Example 2

A similar test to that in Example 1 was performed for concrete mixescontaining 1% by weight, based on the cement content, of water solublevinyl copolymers of solium 2-acrylamido-2-methylpropane sulfonate andacrylamide having different polymerization molar ratios and differentmolecular weights.

The obtained results are shown in Table 3 below.

                  TABLE 3                                                         ______________________________________                                        Sodium 2-                                                                     acryl-                                                                        amido-2-                                                                      methylpro-                                                                             Mole-                        Compressive                             panesulfo-                                                                             cular                        strength                                nate/acryl-                                                                            weight          Trans-       (kg/cm.sup.2)                           amide    (×                                                                              Mixing  mittance                                                                             Slump 7th   28th                              (molar ratio)                                                                          10,000) state   (%)    (cm)  day   day                               ______________________________________                                        Example                                                                        3/97    100     A       75     21.5  256   375                                        300     A       90     21    264   370                                        700     A       100    21    258   375                               10/90    100     A       77     21    257   366                                        300     A       89     21    261   371                                        700     A       99     21    257   370                               20/80    100     A       75     24    256   374                                        300     A       88     23.5  261   377                                        700     A       99     23.5  260   382                               50/50    100     A       74     24    260   378                                        300     A       88     24    263   370                                        700     A       98     23.5  262   382                               85/15    100     A       70     24    255   368                                        300     A       87     24    259   374                                        700     A       98     24    258   379                               Comparative                                                                   Example                                                                        1/99    100     B       76     21    259   360                                        300     B       90     20    260   370                                        700     B       100    20    262   378                               ______________________________________                                    

Example 3

A similar test to that in Example 1 was performed for concrete mixeswhich were obtained by adding a water soluble vinyl polymer compound ofsodium 2-acrylamido-2-methylpropanesulfonate and acrylamide having apolymerization molar ratio of 10:90 and having a molecular weight of7,000,000 to the concrete shown in Table 1. Table 4 below shows theobtained results in relation to the amount of the compound added.

                  TABLE 4                                                         ______________________________________                                        Addition                            Compressive                               amount                              strength                                  (% by weight       Trans-           (kg/cm.sup.2)                             based on  Mixing   mittance  Slump  7th   28th                                cement content)                                                                         state    (%)       (cm)   day   day                                 ______________________________________                                        Example                                                                       0.1       A        89        19     255   368                                 0.5       A        93        22     254   370                                 1.0       A        99        21     257   370                                 2.0       A        100       21     252   367                                 4.0       A        100       21     232   355                                 Comparative                                                                   Example                                                                        0.05     B        60        12     242   350                                 ______________________________________                                    

Example 4

One % by weight of a water soluble vinyl polymer compound having amolecular weight of 7,000,000 used in Example 1 was added to the mortarin Table 5 based on its cement content. The resulting mixture was mixedwith a mortar mixer having a volume of 3 l. The mixed mortar wassubjected to the flow test, the falling through water test and thecompressive strength test.

                  TABLE 5                                                         ______________________________________                                        Unit amounts (kg/m.sup.3)                                                                      Water-cement                                                                              Sand-cement                                      Water  Cement    Sand    ratio (%) ratio (%)                                  ______________________________________                                        338    520       1040    65        200                                        ______________________________________                                    

The flow test was performed in accordance with JIS (Japanese IndustrialStandards) R5201.

According to the falling through water test, a specimen mortar waspoured into a cylindrical container having a diameter of 5 cm and adepth of 5 cm. The test was conducted by placing the test container withthe specimen mortar at a height of 10 cm above the water surface in agraduated measuring cylinder containing 1 l of water. The test resultswere obtained by measuring a turbidity of the water by transmittance ata wavelength of 660 μm with a photoelectric photometer. A highertransmittance means a smaller amount of cement component which has beenseparated from the mortar and diffused into the water, and hence,smaller deterioration of the mortar quality.

Specimens for the compressive strength test were prepared by forming themortar into the form of a square rod having a section of 4×4 cm and alength of 16 cm and then curing it in water at 20° C. The test wascarried out on the 7th and 28th day.

The mixing state of the mortar was indicated in the same manner as inExample 1.

For the purpose of comparison, a similar test was performed for mortarwhich contained 1% by weight of polyacrylamide (molecular weight:7,000,000) based on the cement content. The obtained results are shownin Table 6.

                  TABLE 6                                                         ______________________________________                                                                          Compressive                                                                   strength                                    Water            Trans-           (kg/cm.sup.2)                               soluble vinyl                                                                             Mixing   mittance Flow  7th   28th                                polymer compound                                                                          state    (%)      (cm)  day   day                                 ______________________________________                                        Example                                                                       Sodium 2-acryl-                                                                           A        98       18    260   310                                 amido-2-methyl-                                                               propanesul-                                                                   fonate-acryl-                                                                 amide copolymer                                                               (10:90% mole)                                                                 Comparative                                                                   Example                                                                       Polyacrylamide                                                                            C        92       15    190   250                                 ______________________________________                                    

We claim:
 1. A concrete composition for underwater use consistingessentially of cement, aggregate, water and about 0.1 to 4% by weight,based on the weight of the cement, of a water soluble vinyl polymercontaining vinyl units represented by the formula I: ##STR6## wherein R¹is a hydrogen atom or a lower alkyl group, A is --CH₂ --, --CONHCH₂ --,##STR7## wherein R² and R³ are a hydrogen atom or a lower alkyl groupand can be the same or different, or ##STR8## n is 0 or an integer of 1,and M is a hydrogen atom, alkali metal or ammonium, and containing unitsrepresented by the formula II: ##STR9## wherein R₄ is a hydrogen atom ora lower alkyl group, X is CONH₂, COOR₅ wherein R₅ is a lower alkyl groupor a lower hydroxyalkyl group, or ##STR10## wherein R⁶ and R⁷ are thesame or different lower alkyl group or one of R⁶ and R⁷ is a hydrogenatom and the other is a lower alkyl group, or R⁶ and R⁷ form 5- or6-member rings together with nitrogen atoms bonded thereto, with orwithout oxygen atoms.
 2. A concrete composition for underwater useaccording to claim 1, wherein the water soluble vinyl polymer containingvinyl units having sulfonic groups is a water soluble acryl polymercompound obtained by polymerizing an acryl monomer represented by ageneral formula (III): ##STR11## (wherein R¹, R² and R³ are a hydrogenatom or a lower alkyl group and can be the same or different, and M is ahydrogen atom, an alkali metal or ammonium) with an acryl monomerrepresented by a general formula (IV): ##STR12## (wherein R⁴ is ahydrogen atom or a lower alkyl group).
 3. A concrete composition forunderwater use according to claim 2, wherein the water soluble acrylpolymer compound is a water soluble acryl polymer compound having amolecular weight of not less than 1,000,000 and obtained by polymerizing3 to 95% moles of an acryl monomer represented by the general formula(III) with 97 to 5% moles of an acryl monomer represented by the generalformula (IV).
 4. A concrete composition for underwater use as defined byclaim 1 containing 0.1 to 4% by weight based on the weight of the cementof a water soluble acryl polymer compound having a molecular weight ofnot less than 1,000,000 and obtained by polymerizing 3 to 95% moles ofsodium 2-acrylamido-2-methylpropanesulfonate with 97 to 5% moles of aacrylamide.
 5. A concrete composition for underwater use as defined byclaim 1 containing 0.1 to 4% by weight based on the weight of the cementof a water soluble acryl polymer compound having a molecular weight ofnot less than 1,000,000 and obtained by polymerizing 3 to 95% moles ofsodium 2-acrylamido-2-methylpropanesulfonate with 97 to 5% moles ofN,N-dimethylacrylamide.
 6. A concrete composition for underwater useconsisting essentially of cement, aggregate, water and about 0.1 to 4%by weight, based on the weight of the cement, of a water soluble acrylpolymer obtained by polymerizing an acryl monomer represented by ageneral formula (III): ##STR13## wherein R¹, R² and R³ are a hydrogenatom or a lower alkyl group and can be the same or different, and M is ahydrogen atom, an alkali metal or ammonium, with an acryl monomerrepresented by a general formula (V): ##STR14## wherein R⁴ is a hydrogenatom or a lower alkyl group, and R⁶ and R⁷ are the same or differentlower alkyl group, or one is a hydrogen atom and the other is a loweralkyl group, or R⁶ and R⁷ form 5- or 6-member rings together withnitrogen atoms bonded thereto, with or without oxygen atoms.
 7. Aconcrete composition for underwater use according to claim 6, whereinthe water soluble acryl polymer compound is a water soluble acrylpolymer compound having a molecular weight of not less than 1,000,000and obtained by polymerizing an acryl monomer represented by the generalformula (III) with an acryl monomer represented by the general formula(V).
 8. A method for laying concrete underwater comprising laying aconcrete composition for underwater use consisting essentially ofcement, aggregate, water and about 0.1 to 4% by weight, based on theweight of the cement, of a water soluble vinyl polymer containing vinylunits represented by the formula I: ##STR15## wherein R¹ is a hydrogenatom or a lower alkyl group, A is --CH₂ --, --CONHCH₂ --, ##STR16##wherein R² and R³ are a hydrogen atom or a lower alkyl group and can bethe same or different, or ##STR17## n is 0 or an integer of 1, and M isa hydrogen atom, alkali metal or ammonium, and containing unitsrepresented by the formula II: ##STR18## wherein R₄ is a hydrogen atomor a lower alkyl group, X is CONH₂, COOR₅ wherein R₅ is a lower alkylgroup or a lower hydroxyalkyl group, or ##STR19## wherein R⁶ and R⁷ arethe same or different lower alkyl group or one of R⁶ and R⁷ is ahydrogen atom and the other is a lower alkyl group, or R⁶ and R⁷ form 5-or 6-member rings together with nitrogen atoms bonded thereto, with orwithout oxygen atoms.